Dowel pins on which tooth forms are cast for use in dental models are well known, two of such pins being described or claimed in U.S. Pat. No. 3,277,576 granted on Oct. 11, 1966 to Donald E. Kraft and U.S. Pat. No. 3,521,354 granted on July 21, 1970 to Alfred J. Stern and Harold L. Stern.
Generally, however, the dowel pins heretofor developed have been of machined metal, thus being relatively expensive, or integrally molded of synthetic resin and thus sacrificing some rigidity for economy. The dowel pins also generally have one or more planar surfaces extending the lengths thereof to index the pin upon insertion into the model base and to prevent rotation within the base, this often proving inadequate in preventing rotation especially if the dowel pin is not fully inserted into the base.
In Stern U.S. Pat. No. 3,521,354 a composite metal/plastic structure is described wherein the dowel pin is plastic and comprises a longitudinally tapered body having a shank extending from its wide end with a metal pin inserted in and extending longitudinally from the shank. The pin does not extend through the body and is present to enable mounting the dowel pin directly in the mold and does not enhance structural rigidity.
Accordingly, it is an object of the present invention to provide a novel composite dowel pin that is readily and economically fabricated and which is rugged and simple to use.
It is also an object to provide such a dowel pin having substantial structural rigidity and which permits relatively rapid fabrication of the tooth forms.
Another object is to provide such a dowel pin having a cross sectional configuration that provides improved resistance to rotation upon insertion into the model base.